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Global oil demand is slowly rising as the U.S. and other major economies recover. Inventories of oil and fuel stockpiles in the U.S.—the world's largest oil consumer—have steadily declined from 27-year highs in September. Demand in Latin America and Asia continues to grow as well.

Add to that a slower, steadier rise in oil prices than was seen in 2007-08, and there's a good chance oil can continue to push higher.

"It's an amalgamation of all these countries increasing demand," says Mark Waggoner, president of Excel Futures in Bend, Ore. "A little bit here, a little bit there—when you put it all together, it's a lot."

Some big investors have increased bets that oil prices will continue their ascent. Goldman Sachs, J.P. Morgan and a growing roster of major energy-trading banks expect prices to rise above $100 a barrel in 2011 and stay there. Mr. Waggoner estimates oil could push as high as $130 a barrel next year.

The net long position—or bets futures will rise—of hedge funds and other money managers has nearly tripled since July, according to data from the Commodity Futures Trading Commission.

The last push above $100 a barrel is still fresh on investors' minds. The rally ended in mid-2008, with crude priced at nearly $150. Within three months, however, prices were back below $100 and on their way to a nearly five-year low. The economy was in recession at the time, and prices couldn't hold amid falling consumer spending and a slowdown in manufacturing and global trade.

This time, economists and other market watchers don't expect prices to collapse, partly because the global economy is stronger, but also because the increases have been gradual. Oil futures took all of 2010 to rise from $80 to $90 a barrel; in late 2007, that gap was covered in five weeks. The slower increase has given consumers more time to adjust their household budgets. Also, prices for gasoline and home heating oil two years ago were much higher, which reset expectations about what a steep price increase feels like.

"As long as gasoline prices go up fairly slowly, it's generally not a big problem," says Bill O'Grady, chief market strategist at Confluence Investment Management. U.S. retail gasoline prices, one of the key ways oil prices affect consumers, are up only 8.6% this year, averaging $2.86 a gallon at the end of November.

Traders in crude oil and natural-gas options on the floor of the New York Mercantile Exchange
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Last weekend, ministers from the Organization of Petroleum Exporting Countries agreed to maintain quotas despite the recent oil price rally, signaling that they are comfortable with prices inching toward triple digits. The cartel, which controls about a third of the world's oil output, won't meet again until June 2011.

And an official from Saudi Arabia, the de facto leader of OPEC, said sharp supply drops must accompany prices above $100 a barrel before the group increases production.